In In re Acosta, 19 I. & N. Dec. 211, 1985 WL 56042 (BIA 1985), the BIA analyzed whether the persecution Acosta "fears at the hands of the guerrillas is on account of his membership in a particular social group comprised of taxi drivers and persons engaged in the transportation industry of El Salvador." Id. at 232. Noting that "Congress did not indicate what it understood this ground of persecution to mean," id., the BIA conducted an exhaustive examination of the meaning of the phrase "particular social group." First, the BIA explained that the phrase could be "of broader application" than the other four statutory groups. Id. The Board noted that in "adding the elements in the definition of a refugee," Congress "intended to conform the Immigration and Nationality Act to the United Nations Protocol Relating to the Status of Refugees, to which the United States had acceded in 1968." Id. at 219. Accordingly, the BIA concluded, "it is appropriate for us to consider various international interpretations of that agreement." Id. at 220. By examining these "various international interpretations," the BIA decided that the "notion of a `social group' was considered to be of broader application than the combined notions of racial, ethnic, and religious groups and that in order to stop a possible gap in the coverage of the U.N. Convention, this ground was added to the definition of a refugee." Id. at 232 (citing A. Grahl-Madsen, The Status of Refugees in International Law 76, at 219 (1966)).